FIX: Forefront Threat Management Gateway 2010 prematurely closes the connection to the web server when a web proxy client uploads data by using an SSL tunnel

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Article ID: 2591803 - View products that this article applies to.
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Consider the following scenario:
  • A web proxy client establishes a secure socket layer (SSL) connection to an external web server by using a server that is running Microsoft Forefront Threat Management Gateway 2010.
  • HTTPS inspection is not involved. Therefore, an end-to-end SSL tunnel between the client and the web server is established.
  • Inside this established connection, the client uploads data to the web server.
  • The connection and TCP flow to the web server are slow.

In this scenario, the upload does not finish correctly under certain circumstances.


This problem occurs after the client successfully sends all its data to the TMG proxy server The client does this even though the TMG proxy server has not yet sent all the data to the destination web server because of slow bandwidth between the TMG proxy server and the destination web server.

In this case, the TMG proxy server does not correctly handle the reminding buffer that is to be sent to the destination web server, and the TCP connection is prematurely closed.


To resolve this problem, install the service pack that is described in the following Microsoft Knowledge Base article:
2555840 Description of Service Pack 2 for Microsoft Forefront Threat Management Gateway 2010
Note To enable this hotfix, you must run the setProxySocketSendBufSize.vbs script on the server that is running Forefront Threat Management Gateway 2010.

To have us run the setProxySocketSendBufSize.vbs script for you, go to the "Fix it for me" section. If you prefer to create and run the script yourself, go to the "Let me fix it myself" section.

Fix it for me

To fix this problem automatically, click the Fix it button or link. Then click Run in the File Download dialog box, and follow the steps in the Fix it wizard.

Fix this problem
Microsoft Fix it 50803

  • This wizard may be in English only. However, the automatic fix also works for other language versions of Windows.
  • If you are not on the computer that has the problem, save the Fix it solution to a flash drive or a CD and then run it on the computer that has the problem.

Then, go to the "Did this fix the problem?" section.

Let me fix it myself

To create and run the script, follow these steps:
  1. Start Notepad. To do this, click Start, click Run, type notepad.exe in the Open box, and then click OK.
  2. Paste the following script into the new Notepad file:
    Const SE_VPS_GUID = "{143F5698-103B-12D4-FF34-1F34767DEabc}"
    Const SE_VPS_NAME = "ProxySocketSendBufSize"
    Const SE_VPS_VALUE = 8192
    Sub SetValue()
        ' Create the root object.
        Dim root  ' The FPCLib.FPC root object
        Set root = CreateObject("FPC.Root")
        'Declare the other objects that are needed.
        Dim array       ' An FPCArray object
        Dim VendorSets  ' An FPCVendorParametersSets collection
        Dim VendorSet   ' An FPCVendorParametersSet object
        ' Obtain references to the array object
        ' and the network rules collection.
        Set array = root.GetContainingArray
        Set VendorSets = array.VendorParametersSets
        On Error Resume Next
        Set VendorSet = VendorSets.Item( SE_VPS_GUID )
        If Err.Number <> 0 Then
            ' Add the item
            Set VendorSet = VendorSets.Add( SE_VPS_GUID )
            WScript.Echo "New VendorSet added... " & VendorSet.Name
            WScript.Echo "Existing VendorSet found... value- " &  VendorSet.Value(SE_VPS_NAME)
        End If
        if VendorSet.Value(SE_VPS_NAME) <> SE_VPS_VALUE Then
            VendorSet.Value(SE_VPS_NAME) = SE_VPS_VALUE
            If Err.Number <> 0 Then
                VendorSets.Save false, true
                If Err.Number = 0 Then
                    WScript.Echo "Done with " & SE_VPS_NAME & ", saved!"
                End If
            End If
            WScript.Echo "Done with " & SE_VPS_NAME & ", no change!"
        End If
    End Sub
    Sub CheckError()
        If Err.Number <> 0 Then
            WScript.Echo "An error occurred: 0x" & Hex(Err.Number) & " " & Err.Description
        End If
    End Sub
  3. On the File menu, click Save As, and then save the script as setProxySocketSendBufSize.vbs.
  4. On the File menu, click Exit to exit Notepad.
  5. Double-click the .vbs file that you saved in step 3.

Did this fix the problem?

  • Check whether the problem is fixed. If the problem is fixed, you are finished with this section. If the problem is not fixed, you can contact support.
  • We would appreciate your feedback. To provide feedback or to report any issues with this solution, please leave a comment on the "Fix it for me" blog or send us an email.


Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.


For more information about software update terminology, click the following article number to view the article in the Microsoft Knowledge Base:
824684 Description of the standard terminology that is used to describe Microsoft software updates


Article ID: 2591803 - Last Review: December 21, 2011 - Revision: 4.0
  • Microsoft Forefront Threat Management Gateway 2010 Enterprise
  • Microsoft Forefront Threat Management Gateway 2010 Standard
  • Microsoft Forefront Threat Management Gateway 2010 Service Pack 1
kbfix kbbug kbexpertiseinter kbsurveynew kbfixme kbmsifixme KB2591803

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